Two-stage force multiplier tin snips

ABSTRACT

Two-stage force multiplier tin snips are provided which have a pair of cutting blades and associated tangs, both being pivotable about a cutting axis. Each respective tang is coupled to a pair of handles by a pair of respective tang pins. The handles are pivotably attached to one another about a handle axis. The tin snips provide a mechanism for changing a force multiplier of the cutting blades by selectively adjusting relative longitudinal positioning of the cutting blade axis, the handle axis or the tang pins, relative to another of the cutting blade axis, the handle pins or the tang pins.

BACKGROUND OF THE INVENTION

The present disclosure relates to tin snips. More particularly, theinvention relates to tin snips having a two-stage force multipliercapable of changing the mechanical advantage.

Snips or shears are among the most commonly used hand tools inindustries ranging from sheet metal formation to gardening. Conventionalsnips or shears generally comprise an upper and lower cutting blade,each having elongated handles extending therefrom and attached thereto.The cutting blades are configured to pivot around a single axis pointthat separates the cutting blades from the handles. The cutting motionis activated by applying a constant force to the exterior of thehandles. This exterior force effectively closes the handles.Correspondingly, the cutting blades close around the single axis pointand engage an object to be cut at a variable point along the edges ofthe cutting blades. The force generated at the point of contact betweenthe material being cut and cutting blades is essentially constantthroughout the cutting stroke as the cutting blades are configured topivot around the single axis point.

Mechanical advantage, or the factor by which the force output (i.e.force exerted at the point of contact between the cutting blade andmaterial) is measured relative to the force input (i.e. force exerted onthe handles), is largely important when considering that tin snips andcutting shears have a large range of applications. Accordingly, with alarge range of applications comes an equally large range of cuttingeffort depending on the specific application. For example, cutting forcevaries in the sheet metal forming industry depending on the type ofsheet metal, sheet metal thickness, and sheet metal materialcomposition. When using snips as shrubbery shears, the thickness,durability, and variety of vegetation all determine the required cuttingforce.

For conventional snips or shears having a single point of rotation, themechanical advantage consists of a relatively straight-forwardcomputation. To illustrate the mechanical advantage of conventionalsnips or shears, consider the following unit-less calculation: torque(T)=force (F)*distance (D). In conventional tin snips, an input force isapplied to the handles of the tin snips via a user's hand and thereafteran output force is generated at the point of resistance—i.e. the contactpoint between the cutting blades and material being cut. The distancefrom the above-equation is measured from the input/output force pointsto the single axis point separating the handles and cutting blades.Respective torque equations for the handles and the cutting blades wouldequal: T (handles)=F (input)*D (input) and T (cutting blades)=F(output)*D (output). Accordingly, under the abovementioned principle, T(handles)=T (cutting blades). Thus: F (input)*D (input)=F (output)*D(output). While conventional snips or shears may widely vary in size andshape—consider for this example that the distance between the inputforce point on the handles and the single axis point is 5× longer thanthe distance between the output force at the point of cutting blade andmaterial contact and the single axis point. Therefore: D (input)=5D(output). The equation is thus rearranged to solve for the output force:F (output)={[F (input)*5D (output)]/D (output)}. Therefore: F(output)=5F (input). Here, a user can exert an output force on an objectto be cut that is 5× the input force. In this example, the mechanicaladvantage is largely generated by the difference in the distance D(input) of the handle relative to the distance D (output) of the cuttingblades. Mechanical advantage is important because it enables users toexert higher cutting forces on objects, forces that may otherwise beunobtainable.

A person employing use of the conventional snips or shears having asingle axis point, as in the above example, will require a variety oftools designed for each specific cutting assignment. Tools with longerhandles will be employed for assignments requiring larger output force,while smaller tools having shorter handles will be employed forassignments requiring less output force. Even so, snips or shearsintended to cut harder materials may require unacceptably large amountsof physical input force. Or, alternatively, operation of large tools maybecome overly cumbersome and inoperable due to the long and bulky handlesize.

Thus, there exists a significant need for improved tin snips havingincreased, variable mechanical advantage. Such improved tin snips shouldinclude a two-stage compound mechanism having a sliding adjustment pivotpoint. The mechanical advantage of the tin snips increases by creatingextra handle leverage when sliding the adjustment pivot point from afirst compact position to a second extended position. Such improved tinsnips may also include a mechanism for inverting the handles to providea compact and mobile design. The present invention fulfills these needsand provides further related advantages.

SUMMARY OF THE INVENTION

The present invention is directed to two-stage force multiplier tinsnips having a pair of cutting blades and associated tangs that are bothpivotable about a cutting blade axis. Each respective tang is coupled toa pair of handles by a pair of respective tang pins. The handles arepivotably attached to one another about a handle axis. The two-stageforce multiplier tin snips includes a means for changing a forcemultiplier for the cutting blades by selectively adjusting relativelongitudinal positioning of the cutting blade axis, the handle axis orthe tang pins, relative to another of the cutting blade axis, the handleaxis or the tang pins.

In one embodiment, the tang pins are coupled to the tangs and slidablyreside within a slot formed in each respective handle. Each slotincludes a notch for releasibly retaining the respective tang pin in aretracted position. In this embodiment, the force multiplier is changedby releasing the tang pin from within the notch and thereafter slidingthe tang pin to an opposite end of the slot. Accordingly, the tin snipsmove from a retracted position to an extended position. The tin snipsfurther include a spring associated with each tang for biasing the tangpin toward engagement with the respective notch.

In another alternative embodiment, the tang pins are coupled to thehandles and slidably reside within a slot formed in each respectivetang. Each slot includes a notch for releasibly retaining the respectivetang pin in a retracted position. In this embodiment, the forcemultiplier is changed by releasing the tang pin from within the notchand thereafter sliding the tang pin to an opposite end of the slot.Accordingly, the tin snips move from a retracted position to an extendedposition. The tin snips may also further include a spring associatedwith each tang pin for biasing the handles toward engagement with therespective notch.

Alternatively, the longitudinal location of the cutting blade axis orthe handle axis may be changeable to adjust the mechanical advantage. Inone embodiment, the cutting blade axis slidingly resides within a slotformed intermediate the cutting blades and the tangs. Sliding thecutting blade axis from a first position relatively closer to the tangsto a second position relatively closer to the cutting blades,effectively increases the force multiplier. Alternatively, the handleaxis slidingly resides within a slot formed in each respective handle.Sliding the handle axis from a first position relatively closer to thehandle ends to a second position relatively closer to the cuttingblades, also effectively increases the mechanical advantage.

In another embodiment, the handles of the tin snips may invert to acompact position. In this embodiment, the tin snips include a springtensioned between the tangs for biasing the tin snips in an openposition. Handle inversion may be facilitated by a pair of handle axesinterconnected by a coupler or by means of the pins as slidingly engagedto corresponding angular slots formed in the respective handles. Thehandle axes or angular slots provide the necessary rotational movementsuch that the handles are capable of rotating to an inverted positionrelative to the tangs and cutting blades.

In still yet another embodiment, the tin snips of the present inventionmay include a side cutter. The side cutter may be a traditional compoundleverage side cutter integral to tin snips having a fixed pinarrangement. Or, the side cutter may be integrated into tin snips havinghandles that slide relative to the tangs and corresponding cuttingblades, according to the embodiments described above. When the tin snipsare in an extended position, the side cutter is in an initial engagedposition. Here, a blade on the side cutter is exposed from a handlehousing and is ready for cutting. The side cutter is moved to adisengaged position when the handles and corresponding tangs move fromthe initial extended position to a subsequent compact position. Here,the side cutter is in a disengaged position such that the blade isretracted within the handle housing. Furthermore, the tin snips of thepresent invention may include a selectively engageable lock that securesthe tin snips in a closed position against a means for biasing the tinsnips in an open configuration.

Other features and advantages of the present invention will becomeapparent from the following more detailed description, taken inconjunction with the accompanying drawings, which illustrate, by way ofexample, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate the invention. In such drawings:

FIG. 1 is a top view of the tin snips of the present invention in aclosed compact position;

FIG. 2 is a top view of the tin snips of FIG. 1, in an open compactposition;

FIG. 3 is a top view of the tin snips of FIG. 1, illustrating movementfrom the initial compact position to a subsequent extended position;

FIG. 4 is an alternative top view of the tin snips of FIG. 2, havingonly an upper receiver notch;

FIG. 5 is a top view of the tin snips of FIG. 1, in a disengagedextended position;

FIG. 6 is another top view of the tin snips similar to FIG. 5,illustrating movement from the disengaged extended position to anengaged extended position;

FIG. 7 is a top view of the tin snips of FIG. 1, in an open extendedposition;

FIG. 8 is a bottom view of tin snips embodying the invention and havingtelescoping handles;

FIG. 9 is a bottom view of tin snips having hinged handles;

FIG. 10 is a top view of an alternative embodiment tin snips embodyingthe invention, having slots extending through the handles and the bladetangs;

FIG. 11 is a top view of another alternative embodiment of tin snipshaving intermediate the cutting blades and blade tangs;

FIG. 12 is a top view of inventive tin snips having a lock;

FIG. 13 is a top view of the tin snips of FIG. 12, in an unlocked,closed compact position;

FIG. 14 is a bottom view of the tin snips having a pair of springs,illustrating movement of the handles and cutting blades from an initialclosed compact position to a subsequent open compact position;

FIG. 15 is a bottom view of the tin snips of FIG. 14, in the opencompact position;

FIG. 16 is a bottom view of the tin snips of FIG. 14, in an openextended position;

FIG. 17 is a top view of alternative tin snips allowing slidingadjustment of the handle axis, in an open compact position;

FIG. 18 is a top view of the tin snips illustrated in FIG. 17, in aclosed compact position;

FIG. 19 is a top view of the tin snips illustrated in FIG. 17, in anopen extended position;

FIG. 20 is a top view of the tin snips illustrated in FIG. 17, in aclosed extended position;

FIG. 21 is a top view of an alternative tin snips configuration havinginversed handles, in a locked compact position;

FIG. 22 is a top view of the tin snips illustrated in FIG. 21, in anunlocked compact position;

FIG. 23 is a top view of the tin snips illustrated in FIG. 21, in anopen compact position;

FIG. 24 is a top view of the tin snips illustrated in FIG. 21,illustrating movement from a closed compact position to the open compactposition;

FIG. 25 is a top view of tin snips embodying the invention and havinginversed handles, in a closed compact position;

FIG. 26 is a top view of the tin snips of FIG. 25, illustrating aposition intermediate the compact position and an extended position;

FIG. 27 is a top view of the tin snips of FIG. 25, illustratingengagement of the pins within the upper receiver notches;

FIG. 28 is a top view of the tin snips of FIG. 25, in the compactextended position;

FIG. 29 is another alternate embodiment of the tin snips, incorporatinga coil spring and dual handle pivot points;

FIG. 30 is a top view of the tin snips of FIG. 29, in a closed position;

FIG. 31 is a top view of the tin snips of FIG. 29, illustrating movementof the handles from an inversed position to a standard position;

FIG. 32 is a top view of the tin snips of FIG. 29, in a closed standardposition;

FIG. 33 is a top view of another alternate embodiment of the inventivetin snips, including arched slots incorporated into the handles;

FIG. 34 is a top view of the tin snips of FIG. 32, in a closed inverseposition;

FIG. 35 is a top view of the tin snips of FIG. 32, illustrating handlerotation from the inverse position to a standard position;

FIG. 36 is a top view of the tin snips of FIG. 32, in the closedstandard position;

FIG. 37 is a top view of another alternative form of tin snips, furtherillustrating a side cutter;

FIG. 38 is a top view of the tin snips of FIG. 37, in a closed position;

FIG. 39 is an alternative top view of the tin snips of FIG. 37,illustrating the side cutter integrated into tin snips having slidablehandles;

FIG. 40 is a top view of the tin snips of FIG. 39, in an open engagedposition;

FIG. 41 is a top view of the tin snips of FIG. 39, illustrating the sidecutter exposed from the handle housing when in the closed engagedposition;

FIG. 42 is a top view of the tin snips of FIG. 39, illustrating movementof the side cutter from the engaged position to a disengaged position;

FIG. 43 is a top view of the tin snips of FIG. 39, illustrating the sidecutter residing within a handle housing when in the open disengagedposition; and

FIG. 44 is another top view of the tin snips of FIG. 39, illustratingthe side cutter in a closed disengaged position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in the exemplary drawings for purposes of illustration, thepresent disclosure for tin snips is referred to generally by thereference numeral 40. Turning now to the representative figures in thespecification, FIG. 1 illustrates the tin snips 40 having a set ofpivotably connected handles 42, 44, each having a slot 46, 48 formedtherein. The slots 46, 48 are each adapted to receive a pair of pins 50,52 which are secured to a pair of blade tangs 54, 56. The handles 42, 44move relative to one another about a common handle axis point 58. Thepair of blade tangs 54, 56 are correspondingly configured to pivot abouta base axis point 60 that separates the blade tangs 54, 56 from a pairof cutting blades 62, 64 (shown best in FIG. 2). The cutting blades 62,64 are shown in FIG. 1 in closed form. In this embodiment, the slots 46,48 are formed in the handles 42, 44 and are configured to have the tinsnips 40 operate in a compact position, as shown in FIG. 1, or anextended position as generally shown in FIG. 7. To retain the tin snips40 in either the compact or extended positions, the slots 46, 48 eachhave an upper receiver notch 66, 68 (FIGS. 2-3) and a lower receivernotch 70, 72 (FIGS. 3, 7).

As shown in FIGS. 1 and 2, the pins 50, 52 are engaged in the lowerreceiver notches 70, 72. The pins 50, 52 further engage the lowerreceiver notches 70, 72 when the cutting blades 62, 64 of the tin snips40 are opened. When the tin snips 40 are in the open compact position asillustrated in FIG. 2, both the cutting blades 62, 64 and the handles42, 44 open for the purpose of cutting. The cutting motion is generatedby an input force on the handles 42, 44 along the arrows illustrated inFIG. 2. Applying this force along the handles 42, 44, toward theinterior of the tin snips 40, effectively closes the cutting blades 62,64 upon a material contact point 74. The material contact point 74changes as the cutting blades 62, 64 close and cut the material.

When the tin snips 40 move from an open compact position (FIG. 2) to aclosed compact position (FIG. 1), the handles 42, 44 and the blades 62,64 close. Applying a force along the arrows in FIG. 2 closes the handles42, 44 by pivoting them about the handle axis point 58. In turn, a forceis exerted on the lower receiver notches 70, 72 (not shown in FIG. 2)and transferred to the pins 50, 52. The pins 50, 52, which are connectedto the blade tangs 54, 56, also move to a position substantially closerto one another as the handles 42, 44 close. The movement of the pins 50,52 forces the blade tangs 54, 56 to rotate inwardly. Accordingly, withthe movement of the blade tangs 54, 56, the cutting blades 62, 64 rotateshut about the base axis point 60. During the closing of the cuttingblades 62, 64, an output force is exerted at the material contact point74.

The tin snips 40 also include a second, extended position, wherein themechanical advantage of the force exerted at the material contact point74 is increased. FIG. 3 illustrates the movement of the handles 42, 44from the compact position shown in FIGS. 1 and 2 to an extended positionas shown in FIG. 7. The pins 50, 52 located on the blade tangs 54, 56are removed from the lower receiver notches 70, 72 by exerting anoutward force on the interior of the handles 42, 44 along the interiordirectional arrows as shown in FIG. 3. As the handles 42, 44 extend in adirection along the arrows in FIG. 3, the pins 50, 52 disengage from thelower receiver notches 70, 72. As the handles 42, 44 continue to traveloutwardly, the pins 50, 52 travel through an intermediary section of theslots 46, 48 to the upper receiver notches 66, 68 (FIG. 5). Uponengagement of the pins 50, 52 into the upper receiver notches 66, 68,the tin snips 40 are returned to an operating position by exerting anexternal force on the handles 42, 44 as shown in FIG. 6. FIG. 7illustrates the tin snips 40 in an open extended position and ready forcutting. Notice the increased distance between the handle axis point 58and the base axis point 60 in FIG. 7 relative to FIG. 2. As is furtherherein disclosed, increasing the distance between the handle axis point58 and the base axis point 60 effectively increases the mechanicaladvantage of the tin snips 40.

In an alternate embodiment, the tin snips 40 may include the alternativeslots 46, 48 as shown in FIG. 4. The lower receiver notches 70, 72 arenot necessarily required. The tin snips 40 can operate in the compactposition as shown in FIGS. 1 and 2 without requiring engagement with thelower receiver notches 70, 72. Furthermore, the slots 46, 48 couldinclude multiple receiver notches along the slots 46, 48 to provide morethan two operating positions. The inclusion of more notches along theslots 46, 48 would provide multiple configurations of the tin snips 40,having various lengths and mechanical advantages.

The increased mechanical advantage of the tin snips 40 of FIGS. 1-7 canalso be created via a two-stage composite mechanism wherein the handleaxis point 58 slidably adjusts from the compact position (FIG. 2) to anextended position (FIG. 7). When the distance between the handle axispoint 58 and the base axis point 60 is extended, the mechanicaladvantage of the tin snips 40 is increased. Thus, sliding the handleaxis point 58 from a compact position in FIG. 2 to the extended positionFIG. 7 is comparable to extending the handles 42, 44 to create extraleverage for increased torque.

The kinematic model of the tin snips 40 includes a two-stage forcemultiplier. The first multiplier stage is created by the interaction ofthe handles 42, 44, which rotate about the handle axis point 58, withthe blade tangs 54, 56 via the connection pins 50, 52. The secondmultiplier stage is created by the interaction between the blade tangs54, 56 and the cutting blades 62, 64, which both rotate about the baseaxis point 60. Referring to FIG. 2, the arrows pointing toward thehandles 42, 44 represent the input force location on an external portionof the handles 42, 44 thereof. The handle axis point 58 represents thepivot point between the handles 42, 44. The pins 50, 52 are the forceinput points from the handles 42, 44 to the blade tangs 54, 56 via theslots 46, 48 in the handles 42, 44. As shown in FIG. 2, the base axispoint 60 represents the pivot point between the blade tangs 54, 56 andthe cutting blades 62, 64. The material contact point 74 represents thepoint where the output force from the cutting blades 62, 64 is exertedon a work piece. It is preferred that the handles 42, 44, the slots 46,48, the pins 50, 52, the blade tangs 54, 56, the handle axis point 58,the base axis point 60, and the material contact point 74 are symmetricwith respect to a centerline 76 of the tin snips 40 in FIG. 2.

Alternatively, the tin snips 40 may be configured wherein any of thepoints representing the input force on the handles 42, 44 and/or theplacement of the pins 50, 52 are asymmetric relative to the centerline76 of the tin snips 40. Additionally, the handle axis point 58, the baseaxis point 60, or the material contact point 74 may lie either to theleft side or to the right side of the centerline 76 in FIG. 2.

The force multipliers that create the mechanical advantage of the tinsnips 40 are calculated in two stages. The first stage starts with themagnitude of the input force on the handles 42, 44 along the arrows inFIG. 2. Recall that the force exerted on the handles 42, 44 istransferred via the slots 46, 48 to the pins 50, 52 and thereafter tothe blade tangs 54, 56. The force exerted on the pins 50, 52 iscalculated by multiplying the input force on the handles 42, 44 by theratio of two distances. The first distance is the length between theinput force of the handles 42, 44 to the handle axis point 58 asrepresented by length A in FIG. 7. The second distance is the lengthbetween the handle axis point 58 and the pins 50, 52 as represented bylength B also in FIG. 7. The corresponding force exerted on the pins 50,52 is the input force exerted on the handles 42, 44 multiplied by theratio of the distances A/B. The resulting force of the above equation isutilized as the input force at the pins 50, 52 to compute the secondstage of the two-stage force multiplier tin snips.

The second stage of the two-stage force multiplier tin snips iscalculated similar to the first stage. The input force at the pins 50,52, as calculated above, is similarly multiplied by a length ratio toobtain the output force at the material contact point 74. The firstdistance is the length between the pins 50, 52 and the base axis point60 as represented by letter C in FIG. 7. The second distance is thelength between the base axis point 60 and the material contact point 74as represented by D also in FIG. 7. The output force exerted at thematerial contact point 74 is therefore calculated by multiplying theinput force at the pins 50, 52 by the distance ratio C/D.

The first stage and the second stage force multipliers are then combinedin order to calculate the output force exerted at the material contactpoint 74 relative to the input force on the handles 42, 44 with respectto the distances A, B, C, and D. The ratio between the input forceexerted on the handles 42, 44 and the output force exerted at thematerial contact point 74 is appropriately the mechanical advantage ofthe tin snips 40 of these embodiments. Thus, the force multiplier ormechanical advantage of the embodiments disclosed in FIGS. 1-7 is theforce input multiplied by the ratio of (A*C)/(B*D). The mechanicaladvantage can be increased by increasing either length A or length C; orby decreasing B or length D. The concept behind this force multiplierwas shown in the preceding illustrations as a preferred embodiment. Aperson of ordinary skill in the art will readily recognize thatadjustment of the force multiplier may be obtained by adjusting any ofthe points, including the input force point on the handles 42, 44, thelocation of the pins 50, 52, the location of the handle axis point 58,the location of the base axis point 60, or the location of the materialcontact point 74. Additionally, any of the preceding points may beremoved depending upon the requisite force multiplier configuration inorder to achieve the desired mechanical advantage. Moreover, aspreviously indicated, any of the preceding points may also be alignedasymmetric to the centerline 76 (FIG. 2) of the tin snips 40 of thepresent disclosure. The calculation of the mechanical advantage in thetwo-stage compound mechanism having asymmetric symmetry still onlyrelies on the relative distances as described in the precedingparagraph.

The adjustable movements illustrated thus far are movements only in thevertical direction. Vertical movement of the tin snips 40 is preferredbecause it maintains the material contact point 74 in a substantiallyconstant location. It is this “route” cut point of the cutting blades62, 64 that is maintained (i.e. the points where the cutting blade 62crosses the cutting blade 64). But, it is also possible to adjust any ofthe distances A-D (FIG. 7) in directions that are not entirely vertical,but have, for example, a horizontal component. The calculation of themechanical advantage still relies on the relative distances between allor some of the points previously described.

In the embodiments shown thus far, all of the illustrations have usedstraight slots 46, 48 between two optional notches, the upper receivernotches 66, 68 and the lower receiver notches 70, 72. As is illustratedin FIG. 3, the tin snips 40 have at least two notches to receive thepins 50, 52 in the slots 46, 48 of the handles 42, 44. FIG. 3illustrates stop points only at the upper receiver notches 66, 68 andthe lower receiver notches 70, 72. Alternatively, the slots 46, 48 maybe configured for indexing. For example, the slots 46, 48 may includeadditional notches that are intermittently located along the length ofthe slots 46, 48. Additional notches, single or multiple, provide betteradjustability and a wider range of adjustable mechanical advantages.Additionally, the slots 46, 48 may have other configurations that arenot straight. For example, FIGS. 33-36 illustrate an alternativeembodiment wherein the slots 46, 48 are curved. The slots 46, 48 mayalso be jagged or shaped in another configuration depending on thedesired slot configuration and mechanical advantage. It is also possiblethat the tin snips 40 do not have any slots. For example, the tin snips40 may incorporate relocatable pins that are removed and replacedthrough a hole with a different position (not shown). Moreover, it isalso possible that the tin snips 40 do not use pins 50, 52 at all.Rather, the tin snips 40 may have protrusions on one of the mating partsin recesses of the other mating part that interact in approximaterotation that a pin would normally have accomplished. The matingprotrusion could be adjustable by landing the protrusions in repeatedrecesses in close proximity to one another, like a pawl tooth jumpingfrom one position to the next on a rack gear.

In the embodiments disclosed thus far, the handle axis point 58 and thebase axis point 60 have been stationary, rotatable points that lie onthe centerline 76 of the tin snips 40 (FIG. 2). The handle axis point 58and the base axis point 60 can also be separated so that multiple pointsexist. For example, in FIG. 32, the handle axis point 58 can be replacedwith a pair of handle axis points 78, 80. In a similar manner, the baseaxis point 60 may also be separated into two or more axis points (notshown). In each of the preceding examples, the axis points each reactagainst a common support member that join either of the two pointstogether. A person of ordinary skill in the art will recognize that thetin snips 40 as herein disclosed can embody any set of configurationssuch that distances between any of the axis points may be varied toincrease or decrease the mechanical advantage of the input forcerelative to the output force.

FIGS. 8 and 9 show an alternative embodiment of the tin snips 40 havingextendable handles 42, 44. In FIG. 8, the handles 42, 44 include atelescoping feature wherein the handle length may be extended. FIG. 8generally illustrates the telescoping feature of the handles 42, 44 inthat the standard position of the tin snips 40 is shown in phantomrelative to the subsequent, extended position. The force multiplier iseffectively increased because the distance between the input force onthe handles 42, 44 and the handle axis point 58 is lengthened. Aspreviously described, lengthening this distance (distance A in FIG. 7)increases the mechanical advantage.

A “short snip” design embodying the tin snips 40 uses shorter handlesthan a traditional tin snip, to provide better compactness and mobility.The telescoping feature as disclosed in FIG. 8 enables the “short snip”design to obtain output forces at the material contact point 74 similarto those output forces of traditional sized tin snips. FIG. 9 furtherdiscloses another embodiment for adjusting the force multiplier via thelength of the handles 42, 44. In this embodiment the handles 42, 44 arein a hinged configuration. The handles 42, 44 are initially embeddedwithin the housing of the standard length handles, as shown in phantom,and are extendable by rotating the embedded portion of the handles 42,44 outwardly around the handle pivot points 82, 84. Similar to theconcept in FIG. 8, by increasing the distance between where the inputforce is applied to the handles 42, 44 and the handle axis point 58, theforce multiplier is effectively increased.

Furthermore, FIGS. 8 and 9 disclose a bottom view of the tin snips 40 ofthe present disclosure. A coil spring 86 (shown best in FIG. 29)tensions the blade tangs 54, 56 in an open position, regardless whetherthe tin snips 40 are in the compact position (FIG. 2) or the extendedposition (FIG. 7). In this manner the coil spring 86 travels with themovement of the handles 42, 44. By tensioning the blade tangs 54, 56 ina substantially open position, the cutting blades 62, 64 also remainsubstantially in an open position because the cutting blades 62, 64pivot with respect to the blade tangs 54, 56 around the base axis point60. As further shown in FIGS. 8 and 9, a pair of handle springs 88, 90function to retain the handles 42, 44 in an operable position when thetin snips 40 are moved from a compact position to an extended position,and vice versa. The process of switching the tin snips 40 from a compactposition to an extended position is generally shown through the sequenceof steps starting with FIG. 2 and ending with FIG. 7. When the handles42, 44 are moved substantially outwardly as generally depicted in FIG. 3and FIG. 5, the handle springs 88, 90 exert an inward force along theconnection between the blade tangs 54, 56 and the handles 42, 44 (shownbest in FIGS. 8 and 9). The handle springs 88, 90 provide the forcerequired to return the handles 42, 44 (FIG. 5) to an operable position(FIG. 7). Additionally, the handle springs 88, 90 further facilitateengagement of the pins 50, 52 within the upper receiver notches 66, 68.Subsequently, upon disengagement of the pins 50, 52 from the upperreceiver notches 66, 68, the handle springs 88, 90 are utilized to pullthe pins 50, 52 through the slots 46, 48 to the lower receiver notches70, 72.

In another alternative embodiment as shown in FIGS. 10 and 11, the slots46, 48 can be extended through the handles 42, 44 and through the bladetangs 54, 56 (FIG. 10). In the embodiment in FIG. 10, the cutting blades62, 64 do not move relative to the handles 42, 44. The pins 50, 52 slidein the slots 46, 48 relative to the handles 42, 44, the handle axispoint 58, the base axis point 60, and the material contact point 74.Therefore, the force multiplier is adjusted by changing the distance ofthe pins 50, 52 relative to the aforementioned locations. In thisembodiment, both stages of the two-stage multiplier are affected by themovement of the pins 50, 52. The two-stage force multiplier tin snips 40gains multiplier along stage one, i.e. when the ratio of A/B isincreased (by decreasing length B), while losing multiplier along stagetwo, i.e. when the ratio of C/D is decreased (by decreasing length C),as applicable to FIGS. 17-20 via the distances A, B, C, and Dillustrated in FIG. 7. It is conceived that both multiplier changes maynot offset one another equally. Thus, a net change of the forcemultiplier is still possible within this embodiment and can result ineither an increase in mechanical advantage or a decrease in mechanicaladvantage, depending on the relative distances of A, B, C, and D withrespect to one another.

FIG. 11 further discloses an alternate embodiment of FIG. 10. In thisembodiment, the handles 42, 44 and the blade tangs 54, 56 are only ableto rotate relative to one another about the pins 50, 52. Here, the baseaxis point 60 is slidable within the base slot 92, to adjust the forcemultiplier. In this embodiment, the force multiplier is affected by thedistance between the base axis point 60 and the material contact point74 (length D in FIG. 7) and the distance between the base axis point 60and the pins 50, 52 (length C in FIG. 7).

FIGS. 12-16 illustrate a locking mechanism 94 as used in conjunctionwith the handle springs 88, 90. In FIG. 12, the locking mechanism 94engages a locking pin 96 as shown. Once the locking mechanism 94disengages the locking pin 96 (FIG. 13), the handle springs 88, 90 forcethe handles 42, 44 to an open position as illustrated in FIGS. 14-16.The locking mechanism 94 is typically used to store the tin snips 40.When the locking mechanism 94 is engaged to the locking pin 96, as shownin FIG. 12, the razor edges of the cutting blades 62, 64 are notexposed. Thus, the locking mechanism 94 is used as a safety mechanism toprevent injury during non-use of the tin snips 40.

FIGS. 17-20 further disclose another alternative embodiment of the tinsnips 40 disclosed herein. As best shown in FIG. 20, a set of dualhandle slots 98, 100 replaces the slots 46, 48 shown in FIGS. 1-7. Theadjustability of the mechanical advantage is illustrated by varying thelocation of the handle axis point 58 relative to the force input pointson the handles 42, 44 and relative to the pins 50, 52. The mechanicaladvantage of the tin snips 40 increases when the handle axis point 58moves from an initial position (FIG. 17) to a subsequent position (FIG.19). The output force exerted at the material contact point 74 (notshown in FIGS. 17-20) changes through movement of the handle axis point58. In this embodiment, only the first stage of the two-stage multiplieris affected. By moving the handle axis point 58 from an initial position(FIG. 17) to a subsequent position (FIG. 19), the first stage forcemultiplier is increased as the ratio of the distances A/B (shown in FIG.7) is accordingly increased. The second stage of the two-stagemultiplier is unaffected because the ratio of the distances C/D (FIG. 7)remains constant.

FIGS. 21-24 further illustrate another alternative embodiment whereinthe handles 42, 44 of the tin snips 40 are in an inverted position. Asshown in FIG. 21, the locking mechanism 94, as previously described,effectively retains the inverted handles 42, 44 in a closed positionsuch that the cutting blades 62, 64 also remain closed. Disengaging thelocking mechanism 94 as shown in FIG. 22 enables the coil spring 86 toforce open the inverted handles 42, 44 and the cutting blades 62, 64 asillustrated in FIG. 23. The tin snips 40 are operated by moving thehandles 42, 44 along the arrows illustrated in FIG. 24. As further shownin FIG. 24, the tin snips 40 operate between a closed position and anopen position (in phantom). The tin snips 40 of FIGS. 21-24 are idealfor travel, outdoor use, or military use.

FIGS. 25-28 illustrate the alternate tin snips 40 of FIGS. 21-24, havingthe inversed handles 42, 44, moving from a compact position to asubsequent extended position. The tin snips 40 in FIG. 25 are in theclosed compact position as the pins 50, 52 are engaged in the lowerreceiver notches 70, 72 (not shown) of the slots 46, 48. By widening thehandles 42, 44, as in FIG. 26, the pins 50, 52 disengage the lowerreceiver notches 70, 72 and enter the slots 46, 48. As shown in phantomin FIG. 27, the pins 50, 52 re-engage with the upper receiver notches66, 68 (not shown). After engagement of the pins 50, 52 into the upperreceiver notches 66, 68, the tin snips 40 may be closed as illustratedin FIG. 28. The tin snips 40 are closed by exerting a force along thearrows illustrated in FIG. 28 such that the handles 42, 44 rotate aboutthe handle axis point 58. In turn, the pins 50, 52 move the blade tangs54, 56, which then close the cutting blades 62, 64 about the base axispoint 60. In this embodiment the mechanical advantage changes withrespect to the distance between the input force on the handles 42, 44and the pins 50, 52 and with respect to the distance between the pins50, 52 and the handle axis point 58.

FIGS. 29-32 disclose the tin snips 40 capable of being operated in aninverted position (FIG. 29) or a standard position (FIG. 32). In FIG.29, the handles 42, 44 of the tin snips 40 are in an inverse positionrelative to the blade tangs 54, 56 and the cutting blades 62, 64. Thecoil spring 86 tensions open the blade tangs 54, 56 and the handles 42,44 as connected via the pins 50, 52. The tin snips 40 operate byapplying pressure at the handles 42, 44 along arrows depicted in FIG.29. FIG. 30 discloses the tin snips 40 having the inverse handles 42, 44in a closed position. To invert the handles 42, 44 to a standardposition as shown in FIG. 32, the handles 42, 44 are generally movedalong the arrows illustrated in FIG. 31. The pair of handle axis points78, 80 enable the handles 42, 44 to move in a disjointed manner asfurther depicted in phantom in FIG. 31. Such rotational movement aboutthe pair of handle axis points 78, 80 enable the handles 42, 44 of FIGS.29-32 to move from the inverted position in FIG. 29 to the standardposition in FIG. 32. Once in the standard position the tin snips 40 arecapable of operating in the manner as previously described.

FIGS. 33-36 illustrate an alternate embodiment of the reversible tinsnips 40 as disclosed in FIGS. 29-32. The tins snips 40 of FIGS. 33-36include angled slots 46, 48 to facilitate movement of the handles 42, 44from the inverse position (FIG. 33) to the standard position (FIG. 36).The angled slots 46, 48 as illustrated in FIGS. 33-36 largely do nothave a two-stage mechanical advantage mechanism included therein. But,the angled slots 46, 48 of FIGS. 33-36 could be configured to includethe multiple receiver notches of FIGS. 3 and 26 in order to obtain thereversible and two-stage multiplier characteristics as disclosed herein.

FIGS. 37-44 illustrate yet another alternative embodiment of the tinsnips 40 having a side cutter 102 integrated therein. The side cutter102 includes a blade 104 affixed to a protrusion 106 formed as part ofone of the blade tangs 54, 56. As best shown in FIG. 39, the protrusion106 is formed as part of the blade tang 54. The blade 104 operates witha corresponding base end 108 of the corresponding handle 42. The blade104 may contact the base end 108 to provide a traditional “compoundleverage” fixed pin cutter. The cutting action is initiated bycompressing the handles 42, 44 along the directional arrows shown inFIG. 37, which causes rotation of the handles 42, 44 about the handleaxis point 58. Accordingly, the handles 42, 44 rotate the blade tangs54, 56 via the pins 50, 52 fixed therebetween. Rotation of the handles42, 44 about the handle axis point 58 causes the cutting blades 62, 64to close. As shown in the closed position in FIG. 38, the protrusion 106and the base end 108 rotate toward one another. Cutting is achieved whenthe blade 104 contacts the base end 108. In one embodiment, the cuttingblades 62, 64 comprise jaws, similar to a pair of pliers, and the sidecutter 102 is a wire cutter.

FIGS. 39-44 illustrate an alternative embodiment of the side cutter 102integrated into the tin snips 40. As shown in FIG. 39, the side cutter102 is in an engaged position such that the protrusion 106 andcorresponding blade 104 may contact the base end 108. Again, the handles42, 44 rotate about the handle axis point 58 when compressed toward oneanother along the directional arrows shown in FIG. 39. The integralblade tangs 54, 56 simultaneously close through the coupling of the pins50, 52 residing in respective upper receiver notches 66, 68 formed inthe slots 46, 48 of the handles 42, 44. In turn, the blades 62, 64 closetoward one another about the base axis point 60. Accordingly, in theclosed position as shown in FIG. 40, the protrusion 106 having the blade104 thereon contacts the base end 108 to enable cutting therein.

FIG. 41 illustrates the tin snips 40 further including a pair of handlehousings 110, 112 overlying the handles 42, 44. When the tin snips 40are in the closed position as shown in FIG. 41, the side cutter 102 isexposed from the handle housing 110 and the protrusion 106 and thecorresponding blade 104 are able to contact the base end 108. As will beshown in FIGS. 42-44, the protrusion 106 and the blade 104 may beretracted within the handle housing 110 when the side cutter 102 movesto a disengaged position.

FIG. 42 illustrates movement of the side cutter 102 from an engagedposition, where the protrusion 106 and the blade 104 may contact thebase end 108, to a disengaged position, where the protrusion 106 andcorresponding blade 104 reside within the handle housing 110 and areunable to contact the base end 108. As shown in FIG. 42, the pins 50, 52are disengaged from the upper receiver notches 66, 68 and reside withinthe slots 46, 48 for transition to the lower receiver notches 70, 72.The handles 42, 44 and corresponding handle housings 110, 112 moveforward along the directional arrows shown in FIG. 42 relative to theblade tangs 54, 56 and associated cutting blades 62, 64. The protrusion106 and the blade 104 simultaneously slide back into a channel (notshown) formed at a front end 114 of the handle housing 110 for storagein the disengaged position. Accordingly, the blade 104 is encased andprotected by the handle housing 110 and provides protection frompotential injury as the blade 104 is no longer exposed.

FIG. 43 best illustrates the location of the protrusion 106 and theblade 104 within the handle housing 110. In this embodiment, the sidecutter 102 is in a disengaged position such that movement of the tinsnips 40 to a closed position (FIG. 44) does not result in theprotrusion 106 or the blade 104 contacting the base end 108. Instead,the protrusion 106 and corresponding blade 104 are effectively encasedwithin the handle housing 110. The protrusion 106 and the blade 104simply rotate within the chamber in the handle housing 110 when the tinsnips 40 moves to and from the closed and open positions. The respectivehandle housings 110, 112 may comprise a hard plastic or other softrubber material that allow a user to better grip the tin snips 40.

Although several embodiments have been described in some detail forpurposes of illustration, various modifications may be made withoutdeparting from the scope and spirit of the invention. Accordingly, theinvention is not to be limited, except by the appended claims.

What is claimed is:
 1. Two-stage force multiplier tin snips, comprising:a pair of cutting blades and associated tangs, the blades and tangsbeing pivotable about a cutting blade axis; a pair of handles pivotallyattached to each other at a handle axis, each handle further beingcoupled to a respective tang by a respective pivot slidably residingwithin a slot; a handle housing at least partially overlying a handle ofthe pair of handles; a side cutter having a blade, wherein the handlehousing is selectively retractable such that the blade may be disposedwithin and/or extended out of the handle housing; and a notch associatedwith each respective slot for selectively receiving and locking thepivots therein to prevent sliding movement of the cutting blade axis,the handle axis or the pivots relative to another of the cutting bladeaxis, the handle axis or the pivots while cutting and in order to fixthe cutting blades in a position having a greater force multiplier. 2.Two-stage force multiplier tin snips, comprising: a pair of cuttingblades and associated tangs, the blades and tangs being pivotable abouta cutting blade axis; a pair of handles pivotally attached to each otherat a handle axis, each handle further being coupled to a respective tangby a respective pivot slidably residing within a slot; a notchassociated with each respective slot of a sufficient size so as toselectively receive and lock the pivots therein prior to initiatingcutting action of the tin snips to prevent sliding movement of thecutting blade axis, the handle axis or the pivot relative to another ofthe cutting blade axis, the handle axis or pivots while cutting and inorder to fix the cutting blades in a position having a greater forcemultiplier, a locking force between the notch and the pivot achieved bya spring affixed between the handles and the blade tangs such that whena pivot is received in the notch, the pivot is held in place via theoutward force from the spring; and a side cutter having a blade and aselectively retractable handle housing, wherein the side cutter is in adisengaged position when the handle housing is in an unretractedposition and in an engaged position when the handle housing is in aretracted position.
 3. The tin snips of claim 2, wherein each pivotcomprises a tang pin.
 4. The tin snips of claim 3, wherein each tang pinslidably resides within a slot formed in the respective handle, wherebyadjusting each tang pin within the slot changes the force multiplier.